<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button id="btn4">点击</button>
    <script>
        var btn4 = document.getElementById("btn4");

        btn4.addEventListener("click", hello1);

        btn4.addEventListener("click", hello2);

         

        function hello1() {

             
            alert("hello 1");

        }

        function hello2() {

             
            alert("hello 2");

        }
    </script>
</body>

</html>